The proposed work is aimed at exploring the relative ganglionic and nerve terminal blocking action of cyclic and open chain analogs of dopamine. Also we have discovered 2 hypotensive agents that we believe act by central action. Most of the experimental effort will be directed toward answering the following questions: (1) Do the agents inhibit ganglionic transmission? What is the relative potency at a single ganglionic site? (2) Are there differences in activity at different ganglionic sites? Any correlation with SIF Cell Concentrations? (3) How do these agents differ in pharmacological properties from classical agents? Do the hypotensive agents depress preganglionic sympathetic nerve activity? We have uncovered a rather action - namely inhibition of ganglionic transmission accompanied by adrenergic nerve terminal inhibition. We must evaluate the compounds on induced or normal neural activity in order to evaluate this dual action.